Glass fiber insulation is well known and has been a commercial product for a long period of time. The insulation is made from intertwined soda lime aluminoborosilicate glass fiber which a binder holds together. The binder may be any suitable material but quite commonly is a phenol-formaldehyde resin or a ureaformaldehyde resin. These binders are well known and a spray nozzle generally applies them to the glass fibers as hot gases attenuate the fibers from a rotating device, commonly called a spinner. A conveyo collects the binder-coated fibers in the form of a blanket, and heat cures the blanket to produce the final insulation. The process produces various densities by varying the conveyor speed and the thickness of the cured insulation. This technology is well known.
It is well established that asbestos fibers when inhaled can cause significant disease in man. Though the exact mechanisms responsible for the biological activity of inhaled asbestos fibers is unknown, it is widely believed that their ability to remain in the lung for extended periods of time is an important factor. Glass fibers have not been linked to disease in man. Additionally, their durability or residence time in the lung appears much less than asbestos fibers. Further increasing the solubility of glass fibers would be expected to decrease the time glass fibers will remain in the lung if they are inhaled.
It been known for some time that the dissolution rate of glass fiber in saline solutions similar to those existing in the lung can be significantly increased by altering the chemical composition of the fiber, but it was not obvious that this could be done in such a way that the durability of the fiber insulation for commercial purpose was unimpaired. The present invention describes glass fiber compositions which have increased dissolution rate in physiological saline solutions thought to be similar to those found in the lung but which have adequate durability for commercial insulation applications. Moreover these compositions have physical properties which allow them to be fabricated into glass fiber insulation by the same processes currently used.